The goals of this project are: 1) to continue the refinement of atomic coordinates of the Fab fragment from human myeloma immunoglobulin IgG New, for which a three-dimensional model has been obtained by single crystal X-ray diffraction analysis; 2) to continue the determination of the amino acid sequence and three-dimensional structure of the Fab fragment from human immunoglobulin IgG Hil, a cryoglobulin; 3) to study the three-dimensional structure of the pFc' fragment from guinea pig immunoglobulins (gamma-1). These studies will be carried out using automatic amino acid sequencing and single crystal X-ray diffraction techniques. BIBLIOGRAPHIC REFERENCES: Poljak, R.J., Amzel, M.I., Chen, B.L., Phizackerley, R.P. and Saul, F. Structural basis for the association of heavy and light chains and the relation of subgroups to the conformation of the active site of immunoglobulins. Immunogenetics 2, 39-40 (1975). Poljak, R.M., Amzel, L.M., Chen, B.L., Phizackerley, R.J. and Saul, F. Structure and specificity of antibody molecules. Phil. Trans. R. Soc. London, B, 272, 43-51 (1975).